Audio signals in cinema are caused to be signals of multi-channel structure, and are recorded on the assumption that such multi-channel audio signals are reproduced by speaker units placed at both sides in left and right directions of the screen and speaker units placed at the backward side in left and right directions or both sides in the left and right directions of listener. By reproducing audio signals recorded in the state caused to be of multi-channel structure by a large number of speaker units disposed by a fixed arrangement as stated above, position of sound source within the screen and position of sound image actually heard are in correspondence with each other so that sound field having natural expansion or spreading is established.
When audio signals caused to be of multi-channel structure are also appreciated by using headphone device used in the state affixed on the head portion of listener, sound image is localized within the head of listener, resulting in extremely unnatural sound image localization. Moreover, also similarly in the case where music which does not involve image, etc. is appreciated by the headphone device, sound is heard from within the head unlike the case of speaker reproduction. Thus, in natural sound field is similarly formed, and there result an unnatural reproduction of sound.
Further, since headphone devices conventionally widely used are connected to audio equipment or image equipment through external connection cords, when such headphone device is affixed onto the head portion, connection cord is extended from the head portion. For this reason, it is difficult to obtain satisfactory fitting feeling.
In order to eliminate disagreement of feeling of fitting, etc. resulting from the fact that such connection cord is used, it is conceivable that a transmitting circuit using infrared rays is provided at audio equipment or image equipment adapted to output audio signals, and there is used a headphone device adapted to receive audio signals transmitted from this transmitting circuit by infrared rays to reproduce them.
Meanwhile, in the case where transmission system of audio signals using infrared rays is employed, when screening object of light such as human being passing between infrared ray transmitting unit of audio equipment, etc. and headphone device affixed to the listener is interposed, transmission of audio signals to the headphone device is interrupted, so reproduction sound is interrupted. In addition, when listener who has affixed headphone device walks about, it becomes impossible to precisely and continuously receive infrared rays transmitted from transmitting circuit provided at audio equipment, resulting in the possibility that reproduction sound may be interrupted.